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 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
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package de.blacksheep.jmoteextract.remote.socket.xor;

import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;

class XorInputStream extends FilterInputStream {
  
   /*
    * The byte being used to "decrypt" each byte of data.
    */
    private final byte pattern;
    
    private static final Logger LOGGER =  Logger.getLogger(XorInputStream.class.getName());
  
    /*
     * Constructs an input stream that uses the specified pattern
     * to "decrypt" each byte of data.
     */
    public XorInputStream(InputStream in, byte pattern) {
        super(in);
	this.pattern = pattern;
    }
  
    /*
     * Reads in a byte and xor's the byte with the pattern.
     * Returns the byte.
     */
    public int read() throws IOException {
        LOGGER.log(Level.FINE, "Reading...");
        
        int b = in.read();
        //If not end of file or an error, truncate b to one byte
	if (b != -1)
	  b = (b ^ pattern) & 0xFF;
                     
	return b;
    }
  
    /*
     * Reads up to len bytes
     */
    public int read(byte b[], int off, int len) throws IOException {
        LOGGER.log(Level.FINE, "Reading with offset {0} for {1} Bytes...", new Object[]{off, len});
        
        int numBytes = in.read(b, off, len);

	if (numBytes <= 0)
	    return numBytes;

        for(int i = 0; i < numBytes; i++) {
	    b[off + i] = (byte)((b[off + i] ^ pattern) & 0xFF);
        }
	
	return numBytes;
    }
}